The present invention concerns the sensing of the cross slope of the working tool of a road grader or other surface finishing machine.
In the general case for road surface finishing machines of the road grader type, the slope of the grader blade is not the same as the cross slope, the cross slope being defined as the angle of the road surface with respect to horizontal, measured in a plane perpendicular to the longitudinal direction, i.e., direction of travel. The blade slope and the cross slope are not the same unless the grader blade is positioned in a plane perpendicular to the direction of travel or unless, as in the trivial case, the grader blade, and thus the cross slope, are the horizontal plane. Generally, the actual blade slope is not measured directly because of the adverse physical enviornment at the grader blade. Because there is no place on the grader to mount a slope sensor from which the cross slope can be determined directly, the cross slope must be determined from the blade slope. Mathematically, projecting the blade slope onto a plane perpendicular to the direction of travel yields the true cross slope. It is customary to create a simulated blade slope from which to base the projection.
It is well known in the art to use a control console in the cab of a road grader with means for presetting the slope of the blade and maintaining that slope by servo valves or the like actuated by a pendulum apparatus or its equivalent. The slope sensing device for such systems may be mounted on the blade itself, which reflects true blade slope but not true cross slope.
It is likewise known in the art to have the slope sensing device coupled to a mechanism which computes true cross slope by compensating for the difference between true blade slope and true cross slope. Most of the known methods for performing this computation are extremely expensive, have theoretical built-in errors in their operation, or require exotic, non-standard type mechanical linkages to effect their computation.